ikiwiki supports placing pages in a directory hierarchy. For example,
this page, SubPage has some related pages placed under it, like
LinkingRules. This is a useful way to add some order to your
wiki rather than just having a great big directory full of pages.

To add a SubPage, just make a subdirectory and put pages in it. For
example, this page is subpage.mdwn in this wiki's source, and there is also
a subpage subdirectory, which contains subpage/linkingrules.mdwn. Subpages
can be nested as deeply as you'd like.